A slide screw tuner includes a transmission line in some media, such as coaxial, slabline, waveguide, microstrip, etc. One or more probes can move perpendicular to the center conductor. As a probe moves closer to the center conductor, the mismatch at some frequency will increase, while the mismatch decreases as the probe moves away from the center conductor. At some point, when the probe is far enough away, it has very little effect on the fields around the center conductor, so the transmission line looks nearly like a uniform line without a deliberate mismatch.